We are seeing a behaviour where a field defined in a SQLServer view will not group correctly when read into a dataset via a dataflow. The example below is a date dimension. MonYY is showing one row per day in the month, even though day is not in the visual. Normal behaviour is like YearMonth grouping to a single row per month, that field is also an nvarchar but defined in the base table. This only happens when MonYY is accessed via a dataflow. If you do a get data to the view directly it works correctly. The formats of the fields at the top of the screenshot are identical. Thinking there was some hidden data in MonYY we tried Trim(MonYY) which seemed to fix it, however checking the Len() of the field, it is 6, so nothing hidden. Any ideas why this odd behaviour.
It would be great if you could provide more information. 1. Your version of Power BI Desktop 2. What connection mode are you using to connect to your data source? Is the problem occurring in import mode or directquery mode?